Numerous methods have been suggested and many have been used in an effort to control erosion, and to encourage accretion, of sand and other non-cohesive soils, especially in the instance of beaches--and to discourage deposition of (or to displace) undesired sand or soil, especially in channels useful for shipping. Attempts to overcome undesired effects of wave action or longshore drift, as by construction of groins, jetties, or the like, have usually been unavailing or have produced the opposite of what was sought and/or other deleterious results downdrift therefrom.
Informative articles about beach stabilization include "New Method for Beach Erosion Control" by Machemehl, French, and Huang in Civil Engineering in the Oceans/III (1975) 142-160 and "Experimental Control of Beach Face Dynamics by Water-Table Pumping" by Chappell, Eliot, Bradshaw, and Lonsdale in Engineering Geology, 14 (1979) 21-40--both of which describe how water withdrawal from subjacent beach sand is conducive to deposition of more sand. Vesterby U.S. Pat. No. 4,645,377 teaches such dewatering just below the mean high water level. A somewhat similar test project has been under way at Sailfish Point near Stuart, Florida since the late summer of 1988, with very promising results. All such methods utilize buried piping.
Channel maintenance (or creation) traditionally is accomplished by dredging, repeated whenever wave action or other currents tend to fill in the channel, which is frequently. Dredging costs enough the first time, and necessary repetition is an aggravation of expense. Fluidization as an alternative to dredging is also well recognized, as by Bruun in "Maintaining Tidal Inlet Channels by Fluidization" J. Waterway, etc. Engineering , ASCE, 110(ww4) 117-120; Bruun and Adams in "Stability of Tidal Inlets: Use of Hydraulic Pressure for Channel and Bypassing Stability" J. Coastal Research 4 (1988) 687-701; and by the present inventor with others, especially Weisman and Collins, as in "Fluidization as Applied to Sediment Transport (FAST) as an Alternative to Maintenance Dredging of Navigation Channels in Tidal Inlets" Wastes in the Ocean vol II: Dredged Material Disposal in the Ocean, Kester et al. (eds.) Wiley (1983).
However, even such alternative channel clearing and maintenance have relied upon the energy-intensive step of dredging to enable the necessary piping to be buried preparatory to fluidizing use. Such gross disturbance of the underwater landscape generates additional undesired shifting of non-cohesive subsoils and must be repeated at frequent intervals as nature undertakes to restore the status quo.
The present inventor follows the precept that man has to learn to use nature rather than to fight it in such environmental efforts.
Pipe placement for dewatering and fluidization is disclosed in the present inventor's copending U.S. patent application Ser. Nos. 345,073 filed 28 Apr. 1989, and 465,838 filed 16 Jan. 1990. The prior art is represented by van Steveninck U.S. Pat. No. 3,695,049, in which piping to be buried is supplied with one or more small accompanying pipes to fluidize underlying subsoil "causing the pipeline together with the fluidization pipes to sink into the fluidized seabed"--on the one hand and, on the other hand-- "Pipeline Burial by Fluidization" Paper No. OTC 2276 of OFFSHORE TECHNOLOGY CONFERENCE of the American Institute of Mining, Metallurgical, and Petroleum Engineers at Dallas, Tex. in 1975, wherein a horseshoe-shaped device overlies and straddles piping to be emplaced and fluidizes the adjacent non-cohesive bottom with water jetted from openings in hollow lower stringers of such device, and the piping sags under its weight and the extra weight of the straddling device and sinks into the adjacent fluidized bottom of the subjacent, preferably sandy soil. Clay may interfere with such a goal.
My present invention provides a marriage of onshore dewatering and offshore fluidization, via such piping, for increasing rates of beach accretion and improving the maintenance of existing beaches.